West Coast Groundfish Observer Program Manual, Part2 - NOAA

CHAPTER 6
I. Introduction
Observer programs provide an excellent way to collect
biological specimen information for use by fisheries
biologists and stock assessment analysts. Observers in the
WCGOP are asked to collect fish lengths, weights, sexes,
otoliths, viabilities, tags, and scales in an effort to improve
understanding of various fish stocks.
Fish lengths, sexes and otoliths are used to determine the
relative abundance of fish year classes and the occurrence
of the various year classes in commercial fishing landings.
These specimen collections are also used to estimate the
sexual composition of fish year classes, determine
differential growth rates between sexes, and to provide
length to age ratios for use in stock assessments.
Pacific halibut viabilities (injury data) are used to assess the
mortality rate of Pacific halibut due to commercial fishing.
The injury data collected by Observers are analyzed by staff
from the International Pacific Halibut Commission (IPHC)
and used to estimate yearly mortality rates.
Information from tagged fish and crabs are used by a
variety of educational institutions, state agencies, and
federal agencies. Fish are tagged to study fish migration,
stock separation, fishing related mortality, and population
dynamics. Data from tagged fish is vital to the success of
these studies.
Scales are collected from salmon to verify species
identification. Salmon are often extremely difficult to
identify when caught either because of damage incurred
during gear retrieval or strange coloration due to the
proximity of spawning.
6-2 1/30/2004